Xerographic plate cleaning apparatus



Oct. 18, 1966 F. w. HUDSON 3,273,972

XEROGRAPHIC PLATE CLEANING APPARATUS Filed Sept. 30, 1964 5 Sheets-Sheet 1 INVENTOR FREDERICK W. HUDSON A TTORNEYS Oct. 18, 1966 F. w. HUDSON XEROGRAPHIC PLATE CLEANING APPARATUS 5 Sheets-Sheet 2 Filed Sept. 30. 1964 FIG. 4

INVENTOR FREDERICK W. HUDSON M A T TORNE YS Oct. 18, 1966 F. w. HUDSON 3,273,972

XEROGRAPHIC PLATE CLEANING APPARATUS Filed Sept. 30, 1964 5 Sheets-Sheet 3 FIG. 3

//v VEN TOR FREDERICK W. HUDSON 5V7 AT roRNEYs United States Patent 3 278,972 XEROGRAPHIC PLA'fE CLEANING APPARATUS Frederick W. Hudson, West Henrietta, N.Y., assignor to Xerox Corporation, Rochester, N.Y., a corporation of New York Filed Sept. 30, 1964, Sell. No. 400,488 2 Claims. c1. 1s 30s This invention relates in general to xerography, and in particular, to a xerographic plate cleaning apparatus for the removal of electrostatically adhering particles from a xerographic plate.

In the art of xerography, it is usual to form an electrostatic latent image on a xerographic plate and then to develop this image with an electrostatic attractable powder material, commonly referred to as toner. This developed powder image is then transferred to a copy sheet, such as ordinary paper, and then the xerographic plate is cleaned of any residual powder remaining thereon so that the xerographic plate can be used again for another process step.

In a large number of xerographic reproducing machines now in commercial use, removal of this residual powder is effected by means of a brush cleaning device, employing a cylindrical brush formed of rabbit fur. Brush cleaners of this type are disclosed in US. Patent 2,751,616 and in US. Patent 3,062,109.

Because the photoconductive materials presently used to make xerographic plates are not highly resistant to abrasion, great care has been required in selecting the proper animal pelts from which to make these brushes, and extremely careful processing of these pelts to fabricate the brushes has been required in order to obtain acceptable fur brushes for cleaning the xerographic plates. Attempts have been made for a number of years to substitute synthetic fur brushes for the animal fur brushes, but these attempts in the past had proven ineffective because of excessive matting of the synthetic fibers by the accumulation of toner in the brush fibers as they wipe against the surface of the xerographic plate. In addition, successive scratching of the xerographic plate by these toner loaded synthetic fibers has occurred, and also excessive wear of the brush fibers has occurred as they contact the xerographic drum or by beating against a flicking bar, when used.

It is therefore, the principal object of this invention to improve plate cleaning apparatus whereby synthetic fur cleaning brushes may be employed to clean a xerographic plate of a residual powder.

Another object of this invention is to apparatus whereby an air knife of the cleaning brush of a brush cleaning apparatus.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 illustrates schematically a xerographic apparatus having a brush cleaning device constructed in accordance with the invention;

FIG. 2 is an enlarged view of the brush cleaning device of FIG. 1, as seen from the front of the machine;

FIG. 3 is a right-hand View of the brush cleaning device with the xerographic drum removed, and

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3.

improve cleaning is used to effect cleaning General As shown schematically in FIG. 1, the automatic xerographic reproducing apparatus comprises a xerographic plate 20 including a photoconductive layer or light-receiving surface on a conductive backing and formed in the shape of a drum, which is mounted on a shaft journaled in a frame to rotate in the direction indicated by the arrow to cause the drum surface sequentially to pass a plurality of xerographic processing stations.

For the purpose of the present disclosure, the several xerographic processing stations in the path of movement of the drum surface may be described functionally, as follows:

A charging station, at which a uniform electrostatic charge is deposited on the photoconductive layer of the xerographic drum;

An exposure station, at which a light or radiation pattern of copy to be reproduced is projected onto the drum surface to dissipate the drum charge in the exposed areas thereof and thereby form a latent electrostatic image of the copy to be reproduced;

A developing station, at which a xerographic developing material including toner particles having an electrostatic charge opposite to that of the electrostatic latent image are cascaded over the drum surface, whereby the toner particles adhere to the electrostatic latent image to form a xerographic powdered image in the configuration of the copy being reproduced;

A transfer station, at which the xerographic powder image is electrostatically transferred from the drum surface to a transfer material or a support surface; and,

A drum cleaning and discharge station, at which the drum surface is brushed to remove residual toner particles remaining thereon after image transfer, and at which the drum surface is exposed to a relatively bright light source to eifect substantially complete discharge of any residual electrostatic charge remaining thereon.

The charging station is preferably located, as indicated by reference character A. As shown, the charging arrangement includes a corona charging device 21 which includes a corona discharge array of one or more corona discharge electrodes that extend transversely across the drum surface and are energized from a high potential source and are substantially closed within a shielding member.

Next subsequent thereto in the path of motion of the xerographic drum is an exposure station B. An optical scanning or projection system is provided to project a flowing image onto the surface of the photoconductive drum from a stationary original.

The optical scanning or projection assembly comprises a stationary copy'board which consists of a transparent curved platen member 22 such as, for example, a glass plate or the like, positioned on the exterior of the cabinet, which is adapted to support a document to be reproduced, the document being uniformly illuminated and arranged in light projecting relation to the moving lightreceiving surface of the xerographic drum. Uniform lighting is provided by banks of lamps LMPS arranged on opposite sides of the copyboard. Scanning of the document on the stationary copyboard is accomplished by means of a mirror assembly which is oscillated relative to the copyboard in timed relation to the movement of the xerographic drum.

The mirror assembly, which includes an object mirror 23, is mounted below the copyholder to reflect an image of the document through a lens 24 onto an image mirror 25 which, in turn, reflects the image onto the xerographic drum through a slot in a fixed light shield 26 positioned adjacent to the xerographic drum surface.

Adjacent to the exposure station is a developing station C in which there is positioned a developer apparatus 30 including a casing or housing having a lower or sump portion for accumulating developer material. A bucket type conveyor is used to carry the developing material to the upper part of the developer housing where it is cascaded over a hopper chute onto the xerographic drum to 3 effect development. A toner dispenser 35 is used to accurately meter toner to the developing material as toner particles are consumed during the developing operation.

Positioned next and adjacent to the developing station is the image transfer station D which includes a sheet feeding arrangement adapted to feed sheets of support material, such as paper or the like, successively to the xerographic drum in coordination with the presentation of the devoloped image on the drum surface at the transfer station.

The sheet feeding mechanism includes a sheet feed device 40 adapted by means of vacuum feeders to feed the top sheet, of a stack of sheets on a tray 41, to rollers 42 cooperating with the belts of paper transport 44 for advancing the sheet sufiiciently to be held by paper transport 44 which, in turn, conveys the sheet to a sheet registration device 45 positioned adjacent to the xerographic drum. The sheet registration device arrests and aligns each individual sheet of material and then in timed relation to the movement of the xerographic drum, advances the sheet material into contact with the xerographic drum in registration with a previously formed xerographic powder image on the drum.

The transfer of the xerographic powder image from the drum surface to the sheets of support material is effected by means of a corona transfer device 51 that is located at/or immediately after the line of contact between the support material and the rotating drum. In operation, the electrostatic field created by the corona transfer device is effective to tack the support material electrostatically to the drum surface, whereby the support material moves synchronously with the drum while in contact therewith. Simultaneously with the tack-ing action, the electrostatic field is effective to attract the toner particles comprising the xerographic powder image from the drum surface and cause them to adhere electrostatically to the surface of the support material.

Immediately subsequent to the image transfer stat-ion, there is positioned a stripping apparatus to paper pickoff mechanism 52 for removing the sheets of support material from the drum surface. This device, which is of the type disclosed in Rutkus et al. United States Patent 3,062,536, includes a plurality of small diameter orifices supplied with pressurized aeriform fluid by a suitable pulsator or other device. The pulsator is adapted to force jets of pressurized aeriform fluid through the outlet orifices into contact with the surface of the xerographic drum slightly in advance of the sheet of support material to strip the leading edge of the sheet from the drum surface and to direct it onto endless conveyor 55 whereby the sheet material is carried to a fixing device 60. At the fixing device, the transferred xerographic powder image on the sheet of support material is permanently fixed or fused thereto as by heat. After fusing, the reproduction is discharged from apparatus at a suitable point for collection externally of the apparatus by means of the conveyor 65. In the embodiment shown, the reproductions are discharged from conveyor 65 into a receiving tray 61.

The next and final station in the device is a drum cleaning station E, having positioned therein a corona preclean device 66, a drum cleaning device 70, constructed in accordance with the invention, adapted to remove any powder remaining on the xerographic drum after transfer and a discharge lamp LMP-1 adapted to flood the xerographic drum with light to cause dissipation of any residual electrical charge remaining on the zerographic drum.

Suitable drive means are provided to drive the drum, rotating mirror and sheet feed mechanism at predetermined speeds relative to each other, and to effect operation of the bucket-type conveyor and toner dispenser .mechanism and the other operating mechanisms.

Referring now to the drawings, there is provided a frame for supporting the components of the apparatus formed by a base plate 10 supported on legs 9. Vertical outboard and inboard frame plates 11 and 12 respectively, are secured to base plate 10 in spaced relation to each other.

The xerographic drum 20 is mounted on a horizontal driven shaft and the drum is positioned between frames 11 and 12, with the major xerographic components of the machine mounted around the drum.

It is believed that the foregoing description is sufficient for the purposes of this application to show the general operation of a xerographic reproducing apparatus using a plate cleaning apparatus constructed in accordance with the invention. For further details concerning the specific construction of the xerographic apparatus shown, reference is made to copending application, Serial No 400,363, filed concurrently herewith on September 30, 1964, in the name of R. F. Osborne et al.

Referring now to the subject matter of the invention, the plate cleaning apparatus 70 includes a rotatable brush 71 of such construction so as to apply extremely light pressure to the photoconductive surface of the xerographic plate to dislodge any powder particles that may adhere thereto. This brush, in turn, is cleaned by a flickering bar that is mounted to contact the loose end of the bristles of the brush as it is rotated 'to detach powder particles from the brush. In accordance with the invention, cleaning of the brush is enhanced by the use of an air knife contacting the bristles or fibers of the brush in the area of the flicking bar. The flow of air around and through the pile of the brush will remove loosened powder and the extra air acts to cushion the brush fibers from excessive Wear as they beat on the flicking bar.

Powder particles detached from the brush are removed by a suitable vacuum system. In addition a lamp LMP-l is used to flood the portion of the xerographic plate cleaned by the brush to dissipate any residual electrical charge remaining on the xerographic plate.

Referring now to FIGS. 2, 3 and 4 in particular, the brush 71 includes a cylindrical brush assembly formed of animal fur, or, in view of the present invention, synthetic fur secured to a rigid cylinder, made for example of cardboard.

The brush is rotatably supported in a brush casing which, in the embodiment shown, consists of a right hand end frame 72 and left hand end frame 74 supporting therebetween upper and lower brush shields 76 and 77, respectively, and a vacuum duct 78. Both the right hand and left hand end frames 72 and 74 are provided with semi-circular bosses 73 and 75, respectively, to which the above-described elements are attached, as by screws 79. As shown in FIGS. 2 and 4, the end frames 72 and 74 and the cover 87 to be described are formed with concave edge portions in conformity with the shape of the xerographic drum to permit the casing to be positioned closely adjacent to the xerographic drum while still substantially enclosing the brush.

The brush is supported at its right end, as seen in FIG. 3, by a truncated cone-shaped arbor 81 to support and rotate the brush, the arbor 81 being fixed on the shaft 82 of motor 83 mounted to end frame 72. At its opposite end, the brush is supported by another truncated cone-shaped arbor 84 that is rotatably and movably journaled by bearing 85 on shoulder bolt 86, the threaded portion of which extends through cover 87 and is secured thereto :by nut 88. Bearing 85 and, therefore, arbor 84 are resiliently biased toward the head of bolt 86 by spring 89 encircling the bolt and positioned between bearing washer 91 and cover 87.

Cover 87 is pivotally secured by pin 92 to the reduced bottom portion of end frame 74 and its is releasably secured in position to close the opening in this end frame by screw 93 which threads into a suitable aperture in the end frame. To aid in proper alignment of the cover, a tapered pin 94 extends from the end frame into a suitable aperture formed in the cover.

The vacuum duct 78 is provided with an elongated opening approximately the full length of the brush to permit removal of dust particles and a flicker bar 80 is mounted to an inner wall of the vacuum duct adjacent the opening in interference relation to the bristles of the brush to aid in the removal of powder particles from the brush.

The opening in the opposite end of the vacuum duct is in communication with an exhaust duct 95 secured to the vacuum duct. The exhaust duct 95 is suitably connected to the filter box 96. A filter bag 97 is mounted Within the filter box, with the mouth of the filter bag in communication with the exhaust duct. A motor drive fan unit MOT-6, connected to the filter box, produces a flow of air through the filter box drawing air through the area surrounding the xerographic drum and the dust hood, the air entraining powder particles removed from the drum by the brush as the air flows through the dust hood. Powder particles are separated from the air as it flows through the filter bag so that only clean air is exhausted by the motor driven fan unit.

As shown in FIG. 4, cleaning of the brush bristles as they contact the flicker bar and immediately thereafter is enhanced by means of an air knife, that is air drawn in by the motor driven tfan unit through the gap formed by the left hand edge of the upper brush shield 76, as seen in this figure, and the upstanding portion 78a of vacuum duct 78. Because of the low air pressure area in the exhaust duct and vacuum duct, air is sucked in through the gap and adds to the wind currents surrounding the brush, the air flufling the bristles of the brush and removing loosened powder particles from the brush and eflectively cushioning the bristles as they beat on the flicking bar.

While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth, and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the appended claims.

What is claimed is:

1. In a brush cleaning apparatus for removing electrostatically adhering particles from a xerographic plate wherein a brush is rotatably mounted Within a dust hood in a position wherein a portion of the brush fibers pro ject from an inlet opening in the hood into contact with the surface of the xerographic plate, the dust hood is connected to an exhaust duct, removed from the inlet opening, through which air is drawn out of the dust hood, and a flicker bar is positioned adjacent an opening in the exhaust duct in interference relation to the brush fibers, the improvement including:

means defining an air knife opening in the dust hood removed from the inlet opening and positioned adjacent the flicker bar to direct air flowing into the dust hood, through said air knife opening, over the brush fibers in a direction opposite to the rotation of the brush fibers as they contact said flicker bar. 2. In a brush cleaning apparatus for removing electrostatically adhering particles from a xerographic plate wherein a length of brush is rotatably mounted within a dust hood in a position wherein a portion of the brush fibers project through an inlet opening in the dust hood into contact with the surface of the xer-ographic plate, the dust hood is connected to an exhaust duct removed from said inlet opening through which air is drawn out of the dust hood, and a flicker bar is positioned adjacent the opening in the exhaust duct in interference relation to the brush fibers, the improvement including:

means defining an opening in the dust hood which extends across the length of the rotatable brush adjacent to the flicker bar, said means defining an opening being positioned in the dust hood sufficiently removed from the inlet opening so that the flicker bar is between the opening and the exhaust duct such that air drawn into the dust hood through the opening is directed over the flicker bar to the exhaust duct in a direction opposite to the rotation of the brush fibers.

References Cited by the Examiner UNITED STATES. PATENTS 1,558,717 10/1925 Stukenborg et al. 2,482,781 9/1949 Knowlton et al. 15-308 X 3,062,110 11/1962 Shepardson et a1. -1.7

ROBERT W. MICHELL, Primary Examiner. 

1. IN A BRUSH CLEANING APPARATUS FOR REMOVING ELECTROSTATICALLY ADHERING PARTICLES FROM A XEROGRAPHIC PLATE WHEREIN A BRUSH IS ROTATABLY MOUNTED WITHIN A DUST HOOD IN A POSITION WHEREIN A PORTION OF THE BRUSH FIBERS PROJECT FROM AN INLET OPENING IN THE HOOD INTO CONTACT WITH THE SURFACE OF THE XEROGRAPHIC PLATE, THE DUST HOOD IS CONNECTED TO AN EXHAUST DUCT, REMOVED FROM THE INLET OPENING, THROUGH WHICH AIR IS DRAWN OUT OF THE DUST HOOD, AND A FLICKER BAR IS POSITIONED ADJACENT AN OPENING IN THE EXHAUST DUCT IN INTERFERENCE RELATION TO THE BRUSH FIBERS, THE IMPROVEMENT INCLUDING: MEANS DEFINING AN AIR KNIFE OPENING IN THE DUST HOOD REMOVED FROM THE INLET OPENING AND POSITIONED ADJACENT THE FLICKER BAR TO DIRECT AIR FLOWING INTO THE DUST HOOD, THROUGH SAID AIR KNIFE OPENING, OVER THE BUSH FIBERS IN A DIRECTION OPPOSITE TO THE ROTATION OF THE BRUSH FIBERS AS THEY CONTACT SAID FLICKER BAR. 